What is the likelyhood of a sudden polyp in gallbladder being cancer after colon cancer in person with lynch syndrome?

Size: I know of no relation between lynch syndrome affecting the colon and the gallbladder. Gallbladder polyps are not a "sudden" condition. Small gallbladder polyps are observed & likely only represent cholesterolosis of the lining of the gallbladder. Gallbladder polyps of greater than 1 cm can be resolved with laparoscopic gallbladder surgery.

Low: Because lynch syndrome is caused by defects in dna repair, there is increased risk of cancers not only of the colon and rectum but gastric, bile ducts, prostate, etc. If a newly diagnosed polyp is found in gb, it should be removed to eliminate this possibility. See general or surgical oncologist.

Low but possible: Cancer of the gallbladder is associated with hnpcc/lynch syndrome but, overall most gallbladder polyps are benign. I would speak with your GI doctor as a cholecystectomy may be advised depending on the size and how long it's been there.